Many were badly burned, shaking uncontrollably and left caked in a white substance, injuries which the BBC said suggested the bomb contained something like napalm or thermite.

The headmaster told reporters: "This was the most horrific thing. We have seen images on TV, we have heard many stories, but we have never seen anything like this before.

"The worst thing in life is watching someone die right in front of you and you can't do anything.

"There were dead people, people burning and people running away, but where to? Where would they go? It is not safe anywhere. That is the fate of the Syrian people."

BBC Panorama

A British medic, Dr Rola, who was in Syria with the charity Hand In Hand, treated the victims at the hospital.

She said: "It is just absolute chaos and carnage here. We have had a massive influx of what looks like serious burns, seems like it must be some sort of, not really sure, maybe napalm, something similar to that.

"But obviously within the chaos of the situation it is very difficult to know exactly what is going on."

She added later: "We feel like some sort of, not even a second-class citizen, like we just don't matter. Like all of these children, and all of these people who are being killed and massacred, we don't matter.

"The whole world has failed our nation and it is innocent civilians who are paying the price."

Mohammed Abdullatif, who witnessed the attack, had a message for the United Nations.

"Dear United Nations, you are calling peace, you are calling for peace. What kind of peace are you calling for? Don't you see this, don't you see this? What do you need to see?

"We are just human beings, we want to live. It is our right to live," he said.